997.2 Engine Reliability
03-23-2015, 11:31 AM
#257
You can fry chicken at 300*F, just to put it into perspective.
Thats a blanket statement. Oils vary a ton, especially in their HTHS shear properties. This property is often overlooked in oil comparisons, as modern passenger cars have their oils tested, and rated at 100* C. Above that point most oil manufacturers don't give a damn what the oil does, because they aren't being evaluated there. Your 40 grade oil, thats a 40 grade at 100*c, damn sure won't be a 40 grade at 290F!
So, the oil's ability to maintain viscosity at higher OT is the key to HTHS and how long the oil will live at the elevated temperatures.
I have found that most oils that can be bought over the counter don't like more than 250F for very long. Full-on race oils can sometimes take 300*F for 750 miles of on the hammer driving. The difference is these oils are designed with a dispersant package that fits this bill. Its not something that you can buy at Walmart.
Its my goal to keep OT at 260F or below, but every engine is different, so I use TAN, TBN and Oil Pressure readings to help me evaluate an oil and where it's sweet spot truly is.
I want to stay out of that 275+ range at all costs, and we've done that, even in Grand Am applications. The key is an oil that will live at those temps, and then, further making adjustments to clearances and components so the heat isn't generated in such excess numbers.
Thats a blanket statement. Oils vary a ton, especially in their HTHS shear properties. This property is often overlooked in oil comparisons, as modern passenger cars have their oils tested, and rated at 100* C. Above that point most oil manufacturers don't give a damn what the oil does, because they aren't being evaluated there. Your 40 grade oil, thats a 40 grade at 100*c, damn sure won't be a 40 grade at 290F!
So, the oil's ability to maintain viscosity at higher OT is the key to HTHS and how long the oil will live at the elevated temperatures.
I have found that most oils that can be bought over the counter don't like more than 250F for very long. Full-on race oils can sometimes take 300*F for 750 miles of on the hammer driving. The difference is these oils are designed with a dispersant package that fits this bill. Its not something that you can buy at Walmart.
Its my goal to keep OT at 260F or below, but every engine is different, so I use TAN, TBN and Oil Pressure readings to help me evaluate an oil and where it's sweet spot truly is.
I want to stay out of that 275+ range at all costs, and we've done that, even in Grand Am applications. The key is an oil that will live at those temps, and then, further making adjustments to clearances and components so the heat isn't generated in such excess numbers.
03-23-2015, 11:40 AM
#258
Former Vendor
It'll be advertised as 100C, and the label will state that. All I care about is the viscosity being maintained, as advertised, at the operating temperature that the engine is seeing.
03-23-2015, 11:55 AM
#259
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You can fry chicken at 300*F, just to put it into perspective.
Thats a blanket statement. Oils vary a ton, especially in their HTHS shear properties. This property is often overlooked in oil comparisons, as modern passenger cars have their oils tested, and rated at 100* C. Above that point most oil manufacturers don't give a damn what the oil does, because they aren't being evaluated there. Your 40 grade oil, thats a 40 grade at 100*c, damn sure won't be a 40 grade at 290F!
(...)
Its my goal to keep OT at 260F or below, but every engine is different, so I use TAN, TBN and Oil Pressure readings to help me evaluate an oil and where it's sweet spot truly is.
I want to stay out of that 275+ range at all costs, and we've done that, even in Grand Am applications. The key is an oil that will live at those temps, and then, further making adjustments to clearances and components so the heat isn't generated in such excess numbers.
Thats a blanket statement. Oils vary a ton, especially in their HTHS shear properties. This property is often overlooked in oil comparisons, as modern passenger cars have their oils tested, and rated at 100* C. Above that point most oil manufacturers don't give a damn what the oil does, because they aren't being evaluated there. Your 40 grade oil, thats a 40 grade at 100*c, damn sure won't be a 40 grade at 290F!
(...)
Its my goal to keep OT at 260F or below, but every engine is different, so I use TAN, TBN and Oil Pressure readings to help me evaluate an oil and where it's sweet spot truly is.
I want to stay out of that 275+ range at all costs, and we've done that, even in Grand Am applications. The key is an oil that will live at those temps, and then, further making adjustments to clearances and components so the heat isn't generated in such excess numbers.
I thought that your main concern regarding the 997.2 engine's reliability issues was LOW oil temps not high... did I misunderstand you ?!
The fact his that low mileage engines are WORSE in regard to this failure, because the cylinders are not worn yet! The tighter the running clearances, the more susceptible the engine is to these particular failures. Being worn and loosened up is one way that most engines dodge the bullet when operated in cold climates.
No, not broken in. Well beyond break in, at 20-45K miles, generally.
Being alarmed saves engines. I am only sharing what we see and what we've seen explode in terms of failures in the past 4 months after one of the toughest winters on record. Most of the cars that fail are C4s? Why? Because they perform very well in the snow and ice and are often driven more than any C2 would be in those conditions.
Being alarmed saves engines. I am only sharing what we see and what we've seen explode in terms of failures in the past 4 months after one of the toughest winters on record. Most of the cars that fail are C4s? Why? Because they perform very well in the snow and ice and are often driven more than any C2 would be in those conditions.
03-23-2015, 04:39 PM
#261
Rennlist Member
LOL, give the guy a break. He has already generously shared WAY more info, based on research and first hand experience, then I would expect any business owner would.
If you want to know more, then employ his services. That is how businesses make money to stay alive, and further their research and development.
03-23-2015, 04:54 PM
#262
http://www.elephantracing.com/techto...emperature.htm
03-23-2015, 05:57 PM
#263
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LOL, give the guy a break. He has already generously shared WAY more info, based on research and first hand experience, then I would expect any business owner would.
If you want to know more, then employ his services. That is how businesses make money to stay alive, and further their research and development.
If you want to know more, then employ his services. That is how businesses make money to stay alive, and further their research and development.
But, what do I know, right?! Last time I check I was being called a troll.
03-23-2015, 06:33 PM
#264
Rennlist Member
His statements are not contradictory. The problem is with your comprehension.
It wouldn't matter if the entire m96/m97 Flat6 study guide was posted on here for your review; you would still find something to dispute. This is the nature of the troll.
It wouldn't matter if the entire m96/m97 Flat6 study guide was posted on here for your review; you would still find something to dispute. This is the nature of the troll.
03-23-2015, 08:00 PM
#265
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I couldn't care less about M96/M97 engine issues. This thread is about 997.2 Engine Reliability which has its own specific issues.
Therefore, you can't talk about too high oil temps and low viscosity as the culprit for failing connecting rods at the same time that you talk about too low oil temps and high viscosity as the culprit for the same outcome due to too tight clearances within the same 9A1 kind of engine.
This is a contradiction in terms! Either you have insufficient engine cooling capacity or in excess. Which, in turn, means that either the engine runs too hot or it runs too cool. You can't go wrong both ways!
Moreover, you don't need to run the 9A1 engine at extreme meteorological conditions to observe bore scoring. Experience tells you so!
And last but not the least, disregarding coolant cooling capacity on a water cooled internal combustion engine is like disregarding gender on an heterosexual relationship as long as there is an erection... someone or something will end up getting hurt!
03-24-2015, 12:01 AM
#266
Former Vendor
His statements are not contradictory. The problem is with your comprehension.
I couldn't care less about M96/M97 engine issues. This thread is about 997.2 Engine Reliability which has its own specific issues.
Therefore, you can't talk about too high oil temps and low viscosity as the culprit for failing connecting rods at the same time that you talk about too low oil temps and high viscosity as the culprit for the same outcome due to too tight clearances within the same 9A1 kind of engine.
The high oil temps and loss of viscosity are compounded by high core temperatures of the Alusil engine block, and expansion of the internal clearances. Couple the more open clearances to hotter oil, that has lost viscosity and you have the boom factor. The PWM oil pump does a decent job of boosting OP during these scenarios and saving engines, but it does have a duty cycle and when it hits that point, it can do not more.
On the other end of the spectrum you have a cold engine, with tight internal clearances and pistons that have a rapid expansion coefficient when compared to the cylinders. This creates an opposite issue.
Part of the problem is a lack of material stability across a wide range of operating temperatures from sub zero to above 100 degrees. Being too tight when cold, and too loose when hot pretty much points that out. All it takes is a freezer, and an oven to see these things, and measure what happens. I'd love to build a jig to measure core operating clearances, and one day I might.
This is a contradiction in terms!
Either you have insufficient engine cooling capacity or in excess. Which, in turn, means that either the engine runs too hot or it runs too cool. You can't go wrong both ways!
Moreover, you don't need to run the 9A1 engine at extreme meteorological conditions to observe bore scoring. Experience tells you so!
And last but not the least, disregarding coolant cooling capacity on a water cooled internal combustion engine is like disregarding gender on an heterosexual relationship as long as there is an erection...
Now, anyone who wants to debate viscosity at various temperatures has never seen a Stribeck curve. Myself and Lake Speed Jr. will be going over this very thing in my performance class this coming Saturday. To think an engine runs completely in hydrodynamic lubrication is ridiculous.
In regards to the discussion on DI valve deposits, where do you guys think that the carbon deposits come from up stream of the valve and injectors? Why has Toyota gone to both port injection and DI on the same engine? Oil plays a role in this, and that is why it is part of the new GF-6 oil spec.
That said, the benefit of this thread has diminished, and I believe I am arguing with people about oil that don't even change their own. Sitting around online, hunting through someone's posts from weeks/ months ago, hoping and praying you'll find something to call me out on is also a waste of time. Instead of reading all these articles (most of which were written by people who also don't change their own oil) is also a waste of time. Want to learn? Take your car and do your own analysis, gather your own empirical data and learn something. Just know that if you ever share that knowledge that someone, somewhere is going to bust your ***** for it.
Nothing good will come from more debate on this. I'll keep doing my thing, and you guys can too.
Raby- Out.
03-24-2015, 12:45 AM
#267
Jake ... Thanks.
Wayne
Wayne
03-24-2015, 03:34 AM
#268
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On the other end of the spectrum you have a cold engine, with tight internal clearances and pistons that have a rapid expansion coefficient when compared to the cylinders. This creates an opposite issue.
Part of the problem is a lack of material stability across a wide range of operating temperatures from sub zero to above 100 degrees. Being too tight when cold, and too loose when hot pretty much points that out. All it takes is a freezer, and an oven to see these things, and measure what happens. I'd love to build a jig to measure core operating clearances, and one day I might.
Part of the problem is a lack of material stability across a wide range of operating temperatures from sub zero to above 100 degrees. Being too tight when cold, and too loose when hot pretty much points that out. All it takes is a freezer, and an oven to see these things, and measure what happens. I'd love to build a jig to measure core operating clearances, and one day I might.
An oven?!?! Really?!?!
Do you really believe that you can recreate the thermal load distribution that is happening at different rates in different parts of an internal combustion engine across its operating range with an oven?!
There's no such thing as 'too loose when hot and too tight when cold' as far as piston to cylinder bore clearance is concerned. Once you have too much piston too bore clearance with an hot engine you definitely will have an even greater piston to bore clearance at cold engine - that's when you can more distinctly hear the characteristic 'engine ticking' - because one must allow for piston thermal expansion within the bore.
The problem is not the Alusil bores. The problem can be the DFI system itself, on one hand, and the engine cooling efficiency on the other. Otherwise, how would you explain that cylinder bank #1, and this one specifically, is in fact the most affected?!
Last edited by CaymanPower; 03-24-2015 at 03:54 AM.
03-24-2015, 09:06 AM
#270
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I'm not after money here! On the contrary, I'm just genuinely interested in buying a 997.2 for myself after coming from two consecutive 9A1 bad experiences back in 2010 that ended up on a teared down engine, which is all very well documented on the RL forum and elsewhere, and the last thing I want is to commit the same mistakes all over again.
At first, I thought you could be helpful but I was wrong... that was a mistake! For that I apologize!
My ability to comprehend led me to have mistaken you for a knowledge guy... but soon enough you have enlightened me, that much I can thank you!
It's nothing personal, really.
